Relax checks when reopening devices

When checking whether we are dealing with the same device as before
when we try to reopen it evdev should not require exact match of
entire keymap. Users should be allowed to adjust keymaps to better
match their hardware even after X starts. However we don't expect
changes in [BTN_MISC, KEY_OK) range since these codes are reserved for
mice, joysticks, tablets and so forth, so we will limit the check to
this range.

The same goes for absinfo - limits can change and it should not result
in device being disabled.

Also check the length of the data returned by ioctl and don't try to
compare more than we were given.

[peter: moved the key comparison below the led+abs comparison]

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
(cherry picked from commit a0f7f34dc5effc5822c618bfbf3a0872669c30ad)

1 files changed, 71 insertions, 55 deletions

diff --git a/src/evdev.c b/src/evdev.c
index 0dff271..894aca4 100644
--- a/src/evdev.c
+++ b/src/evdev.c
@@ -1671,6 +1671,7 @@ static int
 EvdevCacheCompare(InputInfoPtr pInfo, BOOL compare)
 {
     EvdevPtr pEvdev = pInfo->private;
+    size_t len;
     int i;
 
     char name[1024]                  = {0};
@@ -1679,107 +1680,122 @@ EvdevCacheCompare(InputInfoPtr pInfo, BOOL compare)
     unsigned long rel_bitmask[NLONGS(REL_CNT)] = {0};
     unsigned long abs_bitmask[NLONGS(ABS_CNT)] = {0};
     unsigned long led_bitmask[NLONGS(LED_CNT)] = {0};
-    struct input_absinfo absinfo[ABS_CNT];
 
-    if (ioctl(pInfo->fd,
-              EVIOCGNAME(sizeof(name) - 1), name) < 0) {
+    if (ioctl(pInfo->fd, EVIOCGNAME(sizeof(name) - 1), name) < 0) {
         xf86Msg(X_ERROR, "ioctl EVIOCGNAME failed: %s\n", strerror(errno));
         goto error;
     }
 
-    if (compare && strcmp(pEvdev->name, name)) {
-        xf86Msg(X_ERROR, "%s: device name changed: %s != %s\n", pInfo->name, pEvdev->name, name);
+    if (!compare) {
+        strcpy(pEvdev->name, name);
+    } else if (strcmp(pEvdev->name, name)) {
+        xf86Msg(X_ERROR, "%s: device name changed: %s != %s\n",
+                pInfo->name, pEvdev->name, name);
         goto error;
     }
 
-    if (ioctl(pInfo->fd,
-              EVIOCGBIT(0, sizeof(bitmask)), bitmask) < 0) {
-        xf86Msg(X_ERROR, "%s: ioctl EVIOCGBIT failed: %s\n", pInfo->name, strerror(errno));
+    len = ioctl(pInfo->fd, EVIOCGBIT(0, sizeof(bitmask)), bitmask);
+    if (len < 0) {
+        xf86Msg(X_ERROR, "%s: ioctl EVIOCGBIT failed: %s\n",
+                pInfo->name, strerror(errno));
         goto error;
     }
 
-    if (compare && memcmp(pEvdev->bitmask, bitmask, sizeof(bitmask))) {
+    if (!compare) {
+        memcpy(pEvdev->bitmask, bitmask, len);
+    } else if (memcmp(pEvdev->bitmask, bitmask, len)) {
         xf86Msg(X_ERROR, "%s: device bitmask has changed\n", pInfo->name);
         goto error;
     }
 
-
-    if (ioctl(pInfo->fd,
-              EVIOCGBIT(EV_REL, sizeof(rel_bitmask)), rel_bitmask) < 0) {
-        xf86Msg(X_ERROR, "%s: ioctl EVIOCGBIT failed: %s\n", pInfo->name, strerror(errno));
+    len = ioctl(pInfo->fd, EVIOCGBIT(EV_REL, sizeof(rel_bitmask)), rel_bitmask);
+    if (len < 0) {
+        xf86Msg(X_ERROR, "%s: ioctl EVIOCGBIT failed: %s\n",
+                pInfo->name, strerror(errno));
         goto error;
     }
 
-    if (compare && memcmp(pEvdev->rel_bitmask, rel_bitmask, sizeof(rel_bitmask))) {
+    if (!compare) {
+        memcpy(pEvdev->rel_bitmask, rel_bitmask, len);
+    } else if (memcmp(pEvdev->rel_bitmask, rel_bitmask, len)) {
         xf86Msg(X_ERROR, "%s: device rel_bitmask has changed\n", pInfo->name);
         goto error;
     }
 
-    if (ioctl(pInfo->fd,
-              EVIOCGBIT(EV_ABS, sizeof(abs_bitmask)), abs_bitmask) < 0) {
-        xf86Msg(X_ERROR, "%s: ioctl EVIOCGBIT failed: %s\n", pInfo->name, strerror(errno));
+    len = ioctl(pInfo->fd, EVIOCGBIT(EV_ABS, sizeof(abs_bitmask)), abs_bitmask);
+    if (len < 0) {
+        xf86Msg(X_ERROR, "%s: ioctl EVIOCGBIT failed: %s\n",
+                pInfo->name, strerror(errno));
         goto error;
     }
 
-    if (compare && memcmp(pEvdev->abs_bitmask, abs_bitmask, sizeof(abs_bitmask))) {
+    if (!compare) {
+        memcpy(pEvdev->abs_bitmask, abs_bitmask, len);
+    } else if (memcmp(pEvdev->abs_bitmask, abs_bitmask, len)) {
         xf86Msg(X_ERROR, "%s: device abs_bitmask has changed\n", pInfo->name);
         goto error;
     }
 
-    if (ioctl(pInfo->fd,
-              EVIOCGBIT(EV_KEY, sizeof(key_bitmask)), key_bitmask) < 0) {
-        xf86Msg(X_ERROR, "%s: ioctl EVIOCGBIT failed: %s\n", pInfo->name, strerror(errno));
-        goto error;
-    }
-
-    if (compare && memcmp(pEvdev->key_bitmask, key_bitmask, sizeof(key_bitmask))) {
-        xf86Msg(X_ERROR, "%s: device key_bitmask has changed\n", pInfo->name);
-        goto error;
-    }
-
-    if (ioctl(pInfo->fd,
-              EVIOCGBIT(EV_LED, sizeof(led_bitmask)), led_bitmask) < 0) {
-        xf86Msg(X_ERROR, "%s: ioctl EVIOCGBIT failed: %s\n", pInfo->name, strerror(errno));
+    len = ioctl(pInfo->fd, EVIOCGBIT(EV_LED, sizeof(led_bitmask)), led_bitmask);
+    if (len < 0) {
+        xf86Msg(X_ERROR, "%s: ioctl EVIOCGBIT failed: %s\n",
+                pInfo->name, strerror(errno));
         goto error;
     }
 
-    if (compare && memcmp(pEvdev->led_bitmask, led_bitmask, sizeof(led_bitmask))) {
+    if (!compare) {
+        memcpy(pEvdev->led_bitmask, led_bitmask, len);
+    } else if (memcmp(pEvdev->led_bitmask, led_bitmask, len)) {
         xf86Msg(X_ERROR, "%s: device led_bitmask has changed\n", pInfo->name);
         goto error;
     }
 
-    memset(absinfo, 0, sizeof(absinfo));
-
-    for (i = ABS_X; i <= ABS_MAX; i++)
-    {
-        if (TestBit(i, abs_bitmask))
-        {
-            if (ioctl(pInfo->fd, EVIOCGABS(i), &absinfo[i]) < 0) {
-                xf86Msg(X_ERROR, "%s: ioctl EVIOCGABS failed: %s\n", pInfo->name, strerror(errno));
+    /*
+     * Do not try to validate absinfo data since it is not expected
+     * to be static, always refresh it in evdev structure.
+     */
+    for (i = ABS_X; i <= ABS_MAX; i++) {
+        if (TestBit(i, abs_bitmask)) {
+            len = ioctl(pInfo->fd, EVIOCGABS(i), &pEvdev->absinfo[i]);
+            if (len < 0) {
+                xf86Msg(X_ERROR, "%s: ioctl EVIOCGABSi(%d) failed: %s\n",
+                        pInfo->name, i, strerror(errno));
                 goto error;
             }
-            /* ignore current position (value) in comparison (bug #19819) */
-            absinfo[i].value = pEvdev->absinfo[i].value;
         }
     }
 
-    if (compare && memcmp(pEvdev->absinfo, absinfo, sizeof(absinfo))) {
-        xf86Msg(X_ERROR, "%s: device absinfo has changed\n", pInfo->name);
+    len = ioctl(pInfo->fd, EVIOCGBIT(EV_KEY, sizeof(key_bitmask)), key_bitmask);
+    if (len < 0) {
+        xf86Msg(X_ERROR, "%s: ioctl EVIOCGBIT failed: %s\n",
+                pInfo->name, strerror(errno));
         goto error;
     }
 
-    /* cache info */
-    if (!compare)
-    {
-        strcpy(pEvdev->name, name);
-        memcpy(pEvdev->bitmask, bitmask, sizeof(bitmask));
-        memcpy(pEvdev->key_bitmask, key_bitmask, sizeof(key_bitmask));
-        memcpy(pEvdev->rel_bitmask, rel_bitmask, sizeof(rel_bitmask));
-        memcpy(pEvdev->abs_bitmask, abs_bitmask, sizeof(abs_bitmask));
-        memcpy(pEvdev->led_bitmask, led_bitmask, sizeof(led_bitmask));
-        memcpy(pEvdev->absinfo, absinfo, sizeof(absinfo));
+    if (compare) {
+        /*
+         * Keys are special as user can adjust keymap at any time (on
+         * devices that support EVIOCSKEYCODE. However we do not expect
+         * buttons reserved for mice/tablets/digitizers and so on to
+         * appear/disappear so we will check only those in
+         * [BTN_MISC, KEY_OK) range.
+         */
+        size_t start_word = BTN_MISC / LONG_BITS;
+        size_t start_byte = start_word * sizeof(unsigned long);
+        size_t end_word = KEY_OK / LONG_BITS;
+        size_t end_byte = end_word * sizeof(unsigned long);
+
+        if (len >= start_byte &&
+            memcmp(&pEvdev->key_bitmask[start_word], &key_bitmask[start_word],
+                   min(len, end_byte) - start_byte + 1)) {
+            xf86Msg(X_ERROR, "%s: device key_bitmask has changed\n", pInfo->name);
+            goto error;
+        }
     }
 
+    /* Copy the data so we have reasonably up-to-date info */
+    memcpy(pEvdev->key_bitmask, key_bitmask, len);
+
     return Success;
 
 error: